Process for killing microorganisms in an aqueous textile finish

ABSTRACT

In a system for the application of a liquid aqueous textile finish, the concentration of living microorganisms in the finish can be held below the level necessitating frequent system cleanups by heating the finish to between 57* C. and about 100* C. for between about 0.1 percent and about 2 percent of the average residence time of the finish in the system.

United States Patent Plischke 1 May 16, 1972 [54] PROCESS FOR KILLING MICROORGANISMS IN AN AQUEOUS TEXTILE FINISH [72] Inventor: LeMoyne W. Plischke, Pensacola, Fla.

] 73] Assignee: Monsanto Company, St. Louis, Mo.

[22] Filed: June 24, 1970 [21] Appl. No.: 49,547

[52] U.S.Cl. ..117/102A, 117/1385, 117/1388 F,

117/1388 N, 117/139.5 CO [51] Int. Cl. ..B05c 11/10 [58] Fieldot'Search ..117/102 A, 1388 F, 138.8 N,

117/138.8 B, 139.5 CQ, 139.5 F, 139.5 C, 138.5; 118/600, 602, 603; 8/147, 158, 159, 137, 141

[56] References Cited UNITED STATES PATENTS 1,154,440 9/1915 Schubert ..8/158 X 2,623,496 12/1952 Lowell ..1 17/102 X 3,093,504 6/1963 Bode ..117/102 2,390,872 12/1945 Dahlberg et al.. 99/215 X 3,031,315 4/1962 Leviton et al.... ..99/215 3,060,093 10/1962 Froscher et a] ..99/215 Primary Examiner-William D. Martin Assistant Examiner-Theodore G. Davis Attorney-Stanley M. Tarter, George R. Beck, Neal E. Willis and Elmer .1. Fischer [5 7] ABSTRACT 10 Claims, No Drawings PROCESS FOR KILLING MICROORGANISMS IN AN AQUEOUS TEXTILE FINISH BACKGROUND OF THE INVENTION It is well known that in conventional systems for the application of a liquid aqueous textile finish to a textile material such as polymeric filaments or fabric made therefrom, it is desirable to maintain the finish prior to such application under conditions which minimize evaporation of water from the finish and/or thermal degradation of the organic constituent or constituents of the finish. In general, those conditions include a temperature below about 42 C. However, there are usually living microorganisms (such as bacteria or fungi) in the finish from contact with the air or other sources and those conditions are normally hospitable to the multiplication of such microorganisms, by which is meant that while the finish is maintained under those conditions, the number of living microorganisms in the finish increases at a substantial rate. If effective measures are not taken to kill a high percentage of the microorganisms in the finish or otherwise greatly inhibit their multiplication, the concentration of the microorganisms in the finish soon reaches a level at which equipment in the finish application system becomes fouled, the finish becomes degraded and/or application of the finish to the textile material becomes uneven resulting in inconsistent and/or undesirable properties of the textile material to which the finish has been applied.

Procedures employed in the past to overcome the problem of excessive microorganism concentrations in aqueous textile finishes have been generally only partially effective or the cause of other difficulties. For example, maintaining the finish at a higher temperature from its preparation until its application to the textile material has significantly inhibited the multiplication of the microorganisms but it has also resulted in undesirable evaporation of water from the finish in some cases. Accordingly, a process effective for killing microorganisms in a system for the application of an aqueous textile finish without causing other substantial difficultiesjs highly desirable and it is an object of this invention to provide such a process.

SUMMARY OF THE INVENTION It has now been discovered that in a system for the application of a liquid aqueous textile finish, the concentration of living microorganisms in the finish can be held below the level necessitating frequent system clean-ups by heating the finish to between about 57 C. and about 100 C. for between about 0.1 percent and about 2 percent of the average residence time of the finish in the system.

DETAILED DESCRIPTION OF THE INVENTION The textile finishes with which this invention is concerned are of the liquid aqueous type which contains at least one organic constituent. They may be solutions but are generally emulsions containing, for example, 12-22 percent by weight of organic constituents. They are conventionally applied to many different textile materials including freshly-spun filaments of various polymeric substances such as polyamides, polyesters, etc., filaments of such substances which have been further processed (e.g. drawn) after being spun and textile products (e.g. woven fabric) made of such filaments. The organic constituents of the finishes can be any of a great variety including antistatic agents, lubricants, wetting agents, coloring agents, etc. See, for example, the finish composition disclosed in US. Pat. No. 3,470,095 which issued to Joseph John Pontclandolfo on Sept. 30, 1969. However, the presence of a particular organic constituent is not critical to the process of this invention. In fact, the invention is applicable to any liquid aqueous textile finish which contains at least one organic constituent, in which microorganisms can live and multiply below about 42 C. and which is substantially resistant to thermal degradation at temperatures within at least a part of the range of from about 57 C. to about 100 C. A great number of such finishes, their uses, systems for their application to textile materials and the problems caused by the presence of living microorganisms in such finishes are well known in the art.

In general, the problem of microorganism multiplication in such finishes is greatest when the finish must be stored for a substantial length of time before it is used, e.g. when it is prepared in batches which are stored for periods of from one hour up to 48 hours or longer. In a typical textile finish application system, the finish containing at least one organic constituent and living microorganisms is circulated from a storage zone to an application zone in which a minor portion of the finish e.g. about 3 to about 20 percent in the case of aspinfinish for freshly spun polymeric filaments) is applied to a textile material and thereon removed from the system. In most cases, the finish on the textile material is thereafter dried leaving at least a portion of the organic constituent or constituents of the finish in solid or semi-solid form on the textile material. The remaining major portion of the finish in the application zone is normally circulated back to the storage zone and the finish applied to the textile material is replaced by addition of fresh finish to the system (generally directly to the storage zone). In most such systems, the average residence time of the finish in the system is at least about one hour and may be as long as two days or longer. In a polymeric filament spin-finish application system, it is usually between about 2 hours and about 10 hours although shorter or longer residence times may be employed. To minimize thermal degradation of the finish and evaporation of water from the finish, the temperature of the finish in such a system is generally maintained near ambient temperature (usually at least about 15 C.) and preferably below about 42 C. However, the microorganisms in such finishes generally multiply rapidly at temperatures below about 42 C. (usually most rapidly between about 32 C. and about 37 C.) and particularly in systems involving recycle of the finish from the application zone to storage, the concentration of microorganisms in the finish typically rises during the aforedescribed residence times to levels which necessitate frequent shutdowns of the system for removal of contaminated finish and/or cleaning of equipment in the system. In systems for the application of a spin-finish to freshly-spun polymeric filaments, those levels are typically on the order of 5-20 million microorganisms per milliliter of finish and the frequency of system shutdowns necessitated thereby is usually on the order of once every 6-7 days.

The surprising discovery of this invention is that even when the finish in the system is maintained at conventional temperatures (i.e., below about 42 C.) for as much as percent or even, in most cases, more than 98 percent of the average residence time of the finish in the system, the concentration of living microorganisms in the finish can be held substantially below such levels, in most cases at levels on the order of about 500,000 microorganisms per milliliter and in many cases at even lower levels by heating the finish in the system to between about 57 C. and about 100 C. for a very small fraction (between about 0.1 percent and about 2 percent and in most cases less than 1 percent) of the average residence time of the finish in the system. The great practical significance of that discovery stems from the fact that the frequency of system shutdowns needed for removal of finish contaminated by the microorganisms and/or cleaning of equipment in the system is thereby typically reduced to once every 3 weeks or even longer.

To minimize thermal degradation of the finish and evaporation of water from the finish, it is usually preferable to heat the finish to relatively low temperatures within the aforementioned 57-100 C. range and for relatively short periods at a time. With some finishes, heating to at least about 57 C. but not above about 75 C. is adequate and desirable although temperatures about 75 C. are satisfactory for other finishes. It is also sufficient (but generally not necessary) to heat the finish to at least about 57 C. for not longer than about 20 seconds (e. g. from 1 to 20 seconds) at a time and above about 42 C. for not longer than about 50 seconds at a time. Such short times above those temperatures generally require that the finish be promptly cooled after it has been heated in accordance with the process of this invention. That can be conveniently accomplished by passing the finish through equipment of any convention type (e.g. shell-and-tube heat exchangers) for heating and then cooling the finish as it is circulated within the system, c. g. from the application zone to the storage zone or, when it is particularly desirable to minimize the concentration of living microorganisms in the finish applied to the textile material, from the storage zone to the application zone.

EXAMPLE I In a conventional system for the application of a spin-finish composed of a 17 weight percent aqueous emulsion of glycerides and ethoxylated esters of fatty acids to freshly-spun polyhexamethylene adipamide filaments, the finish was continuously circulated at the rate of 2.5 gallons per minute from a SO-gallon storage vessel through the tube side of a shell-andtube heat exchanger in which the finish was heated from 35 C. to 65 C. and then through the tube side of a. second shelland-tube exchanger in which the heated finish was cooled to between 35 C. and 40 C. The temperature of the finish as it passed through the exchangers was between 57 C. and 65 C. for between two and three seconds and above 42 C. for between 5 and 6 seconds. From the second exchanger, the finish was continuously circulated to finish pans from which about 6.7 percent by weight of the finish was applied to the filaments and thereon removed from the system. The remaining 93.3 percent by weight of the finish in the pans was continuously circulated back to the storage vessel to which fresh finish was continuously added to replace that withdrawn from the system. The total capacity of the system (storage vessel, finish pans, heat exchangers and connecting circulation lines) was approximately 60 gallons of finish and the average residence time of the finish in the system was about 6 hours. The temperature of the finish was between 57 C. and 65 C. for between 0.14 percent and 0.2] percent and below 42 C. for between 99.58 percent and 99.65 percent of the average residence time of the finish in the system. The concentration of living microorganisms (bacteria) in the finish in the storage vessel was measured by the following procedure. Four-ounce samples of the finish were collected in sterilized bottles, 1-mil liliter portions of the samples were diluted lOO-fold, 1,000- fold and 10,000-fold with sterilized water, one milliliter of each of the diluted portions was mixed in a Petri dish with a liquified bacteria nutrient (Agar; Difco Laboratories) and incubated at 37 C. for 48 hours after which the concentration of bacteria in each culture was read on a Spencer Colony Counter. The concentration readings were found to have a standard deviation of less than 3.2 percent. From daily measurements by that procedure, it was found that throughout several weeks of operation of the system, the concentration of living bacteria in the finish in the storage vessel remained between 300,000 and 525,000 bacteria per milliliter of finish. Over a longer period of operation, it was found that there was no need to shut down the system oftener than once every 3 weeks for clean-ups necessitated by the bacteria in the finish.

EXAMPLE I] When the procedure of Example I is substantially duplicated with the exception that the finish is heated to 60 C., 65 C., 70 C. or 75 C. for between about 0.1 percent and about 2 percent of the average residence time of the finish in the system and the temperature of the finish is below 42 C. for at least percent of that residence time, the results are similar. That is, the concentration of living bacteria in the finish is maintained at a low enough level that the system need not be shut down oftener than once every 3 weeks for cleanups necessitated b6 the bacteria in the finish.

C MPARATIVE EXAMPLE When the procedure of Example I was substantially duplicated with the exception that the finish was not heated above 42' C., the concentration of living bacteria in the finish rose within 2 days to 19,900,000 bacteria per milliliter of finish at which level the system could not be operated satisfactorily.

What is claimed is:

1. In a textile finish application system wherein a liquid aqueous finish containing an organic constituent and living microorganisms is circulated from a storage zone to an application zone, a minor portion of the finish in the application zone is applied to a textile material and thereon removed from the system, the remaining major portion of the finish in the application zone is circulated back to the storage zone, said minor portion of the finish is replaced by addition of fresh finish to the system, the average residence time of the finish in the system is at least about 1 hour and the finish is present in the system under conditions hospitable to the multiplication of said microorganisms including a temperature below about 42 C. for at least about 95 percent of said residence time, the process which comprises heating the finish to between about 57 C. and about C. for between about 0.1 percent and about 2 percent of said residence time.

2. The process of claim 1 wherein the temperature of the finish is below about 42 C. for more than about 98 percent of said residence time.

3. The process of claim 1 wherein the finish is heated to between about 57 C. and about 100 C. for less than about 1 percent of said residence time.

4. The process of claim 1 wherein the finish is heated to between about 57 C. and about 100 C. and then cooled to below about 42 C. as it is circulated from the storage zone to the application zone.

5. The process of claim 1 wherein the finish is heated to between about 57 C. and about 100 C. for not longer than about 20 seconds and above about 42 C. for not longer than about 50 seconds at a time.

6. The process of claim I wherein the finish is heated to at least about 57 C. but not above about 75 C.

7. The process of claim 1 wherein the microorganisms are bacteria or fungi.

8. The process of claim 1 wherein said residence time is between about 2 hours and about 10 hours.

9. The process of claim 1 wherein said minor portion is between about 3 and about 20 percent.

10. The process of claim 1 wherein the textile material comprises freshly-spun polymeric filaments and the finish is a spinfinish for said filaments. 

2. The process of claim 1 wherein the temperature of the finish is below about 42* C. for more than about 98 percent of said residence time.
 3. The process of claim 1 wherein the finish is heated to between about 57* C. and about 100* C. for less than about 1 percent of said Residence time.
 4. The process of claim 1 wherein the finish is heated to between about 57* C. and about 100* C. and then cooled to below about 42* C. as it is circulated from the storage zone to the application zone.
 5. The process of claim 1 wherein the finish is heated to between about 57* C. and about 100* C. for not longer than about 20 seconds and above about 42* C. for not longer than about 50 seconds at a time.
 6. The process of claim 1 wherein the finish is heated to at least about 57* C. but not above about 75* C.
 7. The process of claim 1 wherein the microorganisms are bacteria or fungi.
 8. The process of claim 1 wherein said residence time is between about 2 hours and about 10 hours.
 9. The process of claim 1 wherein said minor portion is between about 3 and about 20 percent.
 10. The process of claim 1 wherein the textile material comprises freshly-spun polymeric filaments and the finish is a spin-finish for said filaments. 